The fine structure of developing weaver cerebella will be continued to be studied from the point of view of dendritic spine development. Reeler cerebella will also be examined. Pathological conditions in the human, especially Menkes' Kinky Hair disease, will be studied by means of electron microscopy of thin sections and light microscopy of Golgi preparations. Special attention will be paid to the pathology of dendritic spine development. BIBLIOGRAPHIC REFERENCES: Hirano, A., and Dembitzer, H.M.: The Fine Structure of Astrocytes in the Adult Staggerer, J. Neuropath. & Exp. Neurol., 35: 63-74, l976. Hanna, R.B., Hirano, A., and Pappas, G.D.: Membrance Specializations of Dendritic Spines and Glia in the Weaver Mouse Cerebellum: A Freeze-Fracture Study. J. Cell. Biol., 68: 403-410, l976.